In confocal optical equipment such as microscopes and spectrometers, the focal point of the illuminating beam path at the output end is located in the focal point of the imaging or detection beam path at the input end. The optical axis of this beam path may coincide with the axis of the illuminating beam path or the two axes may be inclined to one another.
Miniaturized equipment with a confocal arrangement of the illuminating beam path and the detecting beam path are known. Generally the illuminating beam path comprises a light source, a perforated shutter, a collimator, a band pass filter, a dichroic beam splitter and a converging lens. The perforated shutter is located in the focal point of the collimator on the input side. The converging lens images the perforated shutter in the focal point of the illuminating beam path on the output side. The focal point is located on or in the object that is to be examined. The axis of the dichroic beam splitter is tilted relative to the axis of the illuminating beam path.
The detecting beam path starts at the focal point of the converging lens on the output side (confocal imaging). The optical axis of the detecting beam path passes first through the collecting lens at the end of the illuminating beam path; this axis is deflected at the dichroic beam splitter out of the optical axis of the illuminating beam path. The detecting beam path may optionally contain a deflecting mirror. The detecting beam path comprises an edge filter and a collecting lens which collects the light at its focal point on the output side.
If a white or spectrally unclean monochromatic light source is used, the wavelength range which is suitable for exciting the emitted radiation is filtered out using the band pass filter. With the dichroic beam splitter, the light emitted by an object that is to be examined and which is located at the focal point of the illuminating beam path, together with any illuminating light sent back, is deflected. Depending on the nature of the use of the miniaturized spectrometer the edge filter (long pass or short pass filter) is used to filter out the suitable wavelength range in which the wavelength of the radiation emitted by the object that is to be examined is located.
The magnitude of the light source and its heat development require a certain distance between the light source and the miniaturized spectrometer. This distance is generally bridged by an optical fibre. The light is preferably supplied through this optical fibre, the end of which is located at the focal point of the collimator at the entrance to the illuminating beam path.
The light emanating from an illuminated object is preferably supplied from the detection beam path through another optical fibre to the entry slit of the spectrometer. The beginning of the additional optical fibre is located at the focal point of the converging lens at the output from the detecting beam path.
In the spectrometer the spectrum of the radiation emitted by an illuminated object is generated. The spectrum can be visually viewed on a monitor or it can be evaluated and displayed electronically.
DE 100 10 514 (STEAG microparts and Forschungszentrum Karlsruhe) describes an opto-electronic microspectrometer as a hybrid integrated functional unit. The microspectrometer contains an entry slit, a planar waveguide for the incident light and for the spectrally decomposed light, a self-focusing reflection grating and other functional optical elements. The spectrally decomposed light falls on a line of diodes from which the spectrum is supplied to an evaluating unit.
The problem thus arises of providing a miniaturized confocal spectrometer which is significantly smaller than known miniaturized spectrometers and which is as compact as possible in construction. The miniaturized spectrometer should not require any subsequent adjustment by the user. The miniaturized spectrometer should also be suitable for examining objects which contain a small concentration of the substance that is to be detected (molecules or atoms) which will tolerate only a very small dose of radiation or which are sensitive to heat. In addition it should be mobile and capable of being used under extreme conditions and suitable for use by untrained people.